Foundry mold



June 20, 1939. v w w. COOPER 3 2,163,373

FOUNDRY MOLD Original Filed July 2, 1937 2 sheets-sheet 1 June 20, 1939. w. w. COOPER FOUNDRY MOLD 2 Sheets-Sheet Original Filed July 2; 1937 Patented June 20, 1939 UNITED STATES FOUNDRY MOLD William W. Cooper,. Harrisburg, Pa., assignor to Bethlehem Steel Company, a corporation of Pennsylvania,

Application July 2, 1937, Serial No. 151,558 Renewed May 4, 1939 6 Claims.

This invention relates to improvements in molds and cores for metal casting. I Sand molds and cores which have long been almost universally used in iron and steel foundries, have certain disadvantages, well known to those engaged in foundry work. For example; sand molds require baking in order to dry them before use. This means considerable expense for furnaces and heat. Furthermore, the preparation of sand molds is a highly skilled operation, thus requiring the employment of high priced workmen. Again, even the best of sand molds do not possess much inherent structural strength, and are thus not susceptible of much handling. ll On the other hand, sand-cement molds and cores of the type now well known in the art succeed in eliminating many of the objectionable features of the sand type. By the expression sand-cement molds and cores as used in this specification, I refer to molds and cores formed of a mixture of sand, hydraulic cement and sufficient water to allow the mixture to be molded into any desired shape.

Sand-cement molds, as is well known, do not require baking before use. They do not involve the use of heavy and expensive flasks, as the mixture possesses suflicient strength in itself to hold its shape without external reinforcement. They are structurally very strong, and can be handled and moved about without fear'of their cracking.

At the same time, there were certain disadvantages inherent in the use of sand-cement molds and cores as they have been heretofore employed, which it is one of the objects of this invention to eliminate. The amount of hydraulic cement used has considerably increased the cost. thermore, the unyielding character of prior sandcement molds and cores has increased the danger of breaking the castings. A core, for example, has frequently been -so rigid that it would not give to permit contraction of a casting around the core. The danger of the casting breaking under such a condition is easily apparent.

vI have discovered that by making a portion or portions of the mold or core of the sandcement mixture and another portion or portions of sand, I am able to obtain the advantages of a sand-cement mold or core while at the same time lessening, if not entirely eliminating, the undesirable -or objectionable features above mentioned. To that end my invention comprises molds or cores having a section or sections of sand-cement mixture and a section or sections Fur-- of sand, the section of sand-cement mixture being of suflicient dimensions to give the molds v or cores the strength necessary for handling but insufficient to impart such rigidity as to prevent the molds or cores from yielding readily when subjected to the forces imposed by the shrinking castings. I have found that with this combination I am able to obtain the optimum strength without excessive rigidity. At the same time, by eliminating a considerable portion of the cement heretofore required, I succeed in effecting a substantial saving in the cost.

Briefly, then, it is an object of this invention to provide molds and cores formed of a combination of sections or parts of sand-cement and sand so as to obtain all of the advantages of sand-cement and to eliminate substantially all of its disadvantages.

The above and other objects of my invention, and the novel features thereof, will be more fully understood from the following description and claims taken with the drawings, in whch Fig. 1 is a side elevation of a core for a hollow casting, and embodying one of the features of my invention;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a section on the line 33 of Fig. 1;

Fig. 4 is a plan view of a mold embodying my invention; and

Fig. 5 is a section on the line 5-5 of Fig. 4.

Referring to Figs. 1, 2 and 3, the core there illustrated is made up of bottom section III, intermediate section II and top section I2. Section I0 is formed of sand-cement, section II of ordinary unbonded sand and section I2 of green sand. Embedded longitudinally in section 10 are a number of metal reinforcing bars l3. Spaced at intervals through the core are circular metal bands or hoops l4. While the bars l3 and hoops II are not an essential part of my invention, it can easily be seen that they assist in securing a stronger and. more coherent structure. Adjacent each end of the core is a semi-circular metal band l5. As shown in Fig. 1, I preferably at least partially close over the ends of the core with sand-cement in order to seal in the sand of section II.

In the process of forming the core, I embed therein eye-bolts l6, whose bottom hooks ll engage semi-circular bands IS. The purpose of bolts 16 of course is to permit of the core being moved about by a crane or like. machine, having books which will engage eye-bolts l6.

The advantages of a core constructed in this manner will be at once appreciated by foundry men. The sand-cement section 10 gives to the core suflicient structural strength to permit of its safe handling without breaking. Sand section ll, containing no binder, or substantially no binder, and section l2, which contains a binder such as clay, require no cement, and therefore the cost of the core is greatly reduced. This saving is effected without any loss of the advantages due to the use of the sand-cement mixture, as I have found that the core receives suflicient strength from the sand-cement section I0, section l0 being of such thickness as to offer great enough rigidity to enable the core to be handled. Being the lower or supporting section of the core, this relatively rigid section In efl'ectively sustains the weight of the core as-a whole when it is being handled.

When the core has dried in air, and the moisture in the sand of section H has passed. off, the dried unbonded sand will occupy less space than it did while it was moist. This is an important feature of my invention because the core will now possess more yieldability and will permit the casting to contract as much as necessary without undue resistance by a rigid core, with a decreased tendency to cracking of the casting. The core is compressible by reason of the reduced volume of the internal sand section.

Referring now to Figs. 4 and 5, there is illustrated a mold 20 embodying my invention. The walls 2| of this mold are built of a fairly thick layer of sand-cement. Theinterior of the mold is filled with plain moist sand 22 (with no other binder except water). Walls 2| are of a thickness to impart sufficient strength to the mold to permit of it being handled. But little strength is imparted to the mold by the sand 22. As the mold dries out, after its manufacture, the sand 22 contracts. As a consequence, the mold, when ready for use, is considerably more yielding in character than if the mold as a whole'were made of the sand-cement mixture. The thickness to be selected for the walls 2| will vary with the size of the casting. It must always be of such thickness to enable the mold to be handled but the thickness should not be great enough to render the mold so rigid that it does not yield readily during contraction of the castings. Moreover, the thickness should not greatly exceed.

that necessary to give the mold suflicient strength as otherwise the cost of the mold is increased.

In both the core and mold above described, the removal thereof from a casting after solidification is greatly facilitated by my form of construction. The dried unbonded sand flller in both cases will run out easily, leaving only a relatively small mass of sand-cement to be removed from the casting. Further, the sand filler gives greater permeability to cores and molds than ,would those of solid sand-cement.v

Where cores of irregular shapes or of comparatively small size are needed, it may be found desirable to make the-entire exterior of the core of sand-cement, filling the interior with moist sand. This, however, is a matter to be determined in individual instances in accordance with the best judgment of the founder in the. prac tice of this invention in its broader aspect.

Hereafter in the claims, where I use the term mold I intend the term to be used broadly in the sense of either a mold proper or a core.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a foundry mold, a section comprising sand and cement, and a section of sand, the first mentioned section being of such thickness that it has sufficient rigidity to sustain the weight of the mold when being handled.

2. In a foundry mold, an exterior section comprising sand and. cement and an interior section prising sand and cement of suflicient thickness and rigidity to sustain the weight of the mold when being handled, an interior section consisting substantially of sand, said exterior section constituting at least a part of the bottom of the exterior of the mold.

5. In a foundry mold, an exterior section comprising sand and cement, and an interior section of substantially unbonded sand.

6. In a foundry core, a section of sand-cement mixture involving a part of the exterior of the core, a section of green sand involving another part of the core, and a section of substantially unbonded sand enclosed by the two first men'- tioned sections.

WILLIAM W. COOPER. 

